There has been commonly known an air conditioner as disclosed in Japanese Patent Application Open Gazette No. 4-251158. The air conditioner has a refrigerant circulating circuit in which a compressor, a four-way selector valve, an outdoor heat exchanger, a rectification circuit, an indoor heat exchanger and an accumulator are connected in this order and which is reversibly operatable between a cooling operation cycle and a heating operation cycle. The rectification circuit has four delivery valves, a motor-operated expansion valve and a receiver located on an upstream side of the expansion valve.
In the refrigerant circulating circuit, during the cooling operation cycle, the outdoor heat exchanger condenses refrigerant transmitted from the compressor, the motor-operated expansion valve reduces the pressure of the refrigerant and then the indoor heat exchanger evaporates the refrigerant. 0n the other hand, during the heating operation cycle, the four-way selector valve is switched over, the indoor heat exchanger condenses refrigerant transmitted from the compressor, the motor-operated expansion valve reduces the pressure of the refrigerant and then the outdoor heat exchanger evaporates the refrigerant.
In the above-mentioned air conditioner, the receiver is provided on a high-pressure line into which high-pressure refrigerant flows all the time and the accumulator is provided on the intake side of the compressor so that surplus refrigerant in the heating operation cycle is stored in the receiver. At a transient time to a steady state in the cooling and heating operation cycles, liquefied refrigerant flowing toward the compressor is removed by the accumulator, thus preventing the liquefied refrigerant from returning to the compressor.
In the air conditioner, however, the accumulator is provided in the refrigerant circulating circuit, which invites increase in devices. Further, pressure loss in the accumulator deteriorates running performance of the air conditioner.
When the accumulator is merely removed from the refrigerant circulating circuit, the receiver has only one function of storing refrigerant and cannot regulate a circulating amount of refrigerant. This reduces an allowance range of a charge amount of refrigerant.
Furthermore, since the rectification circuit is provided in order that the receiver can be set on the high-pressure line all the time, four delivery valves are required. This increases the number of elements and rises the cost of the air conditioner.
It may be considered that the refrigerant circulating circuit is so composed that the refrigerant flows toward the motor-operated expansion valve in both directions. In this case, however, in an operation cycle in case where the receiver is located on a low-pressure line, for example, in the cooling operation cycle in case where the receiver is provided between the motor-operated expansion valve and the indoor heat exchanger, the receiver cannot store liquefied refrigerant of high pressure. Accordingly, the air conditioner cannot cope with a pressure rising of high-pressure refrigerant.
This invention has been made in view of the foregoing problems. The invention has its objects of extending an allowance range of a charge amount of refrigerant and coping with a pressure rising of high-pressure refrigerant, while reducing the number of elements.